A user interface is a portion of a program with which a user interacts. Types of user interfaces include, but are not limited to, command-line interfaces, menu-driven interfaces, and graphical user interfaces (“GUIs”). A windowing environment is a type of GUI that presents the user with specially delineated areas of the screen called windows that may be resized and moved around on the display of a computer. The Macintosh OS® and Microsoft Windows® are both examples of windowing environments that provide means for a user to interact with an application. Those skilled in the art and others will recognize that, increasingly, application programs are designed for windowing environments to assist user in performing task(s), such as word processing, accounting, database management, and the like.
Modem operating systems are primarily windowing environments that present graphical elements as opposed to purely textual elements. Typically, application programs employ graphical elements derived from the operating system which results in a common “look and feel” between the different application programs installed on the same computer. Commonly used GUI elements include, but are not limited to, menus, buttons, check boxes, scroll bars, listboxes, comboboxes, and the like. Those skilled in the art and others will recognize that each GUI element is presented as an image composed of pixels on a computer display. Moreover, generally described, different GUI elements provide alternative ways for presenting and/or interacting with the user. For example, check boxes are designed to obtain Boolean-type input from a user in that a property displayed in the checkbox is in one of two possible states (e.g., selected or unselected). By way of another example, a listbox will typically present different variables in a list of items, any of which may be selected by the user. Thus, a variety of GUI elements may be presented to a user in a windowing environment depending on the type of input that is needed.
As GUIs have become ubiquitous, many object-oriented tools were developed that facilitate the use of GUI elements in a program. In some operating systems, a GUI element is defined as a class from which objects or instances of the class may be created. Moreover, data presented to the user in a GUI element is typically stored in a underlying data store that allows relationships to be defined between the data. When a GUI element is scheduled to be displayed to the user, an object or other program code retrieves data from the data store. For example, in the case of a listbox, a plurality of data items may be retrieved from a data store and displayed as variables in the listbox. In this example, the data retrieved from the data store is referred to as being “bound” to the GUI element in which the data is displayed.
In existing systems, once a GUI element has been displayed, the user is unable to easily add or otherwise modify data items presented in the GUI element. For example, data may be retrieved from an underlying data store for display in a GUI element that is user-defined metadata. In this example, the metadata will typically be obtained and stored in the data store using a previously executed process or program. Moreover, when the metadata is displayed to the user in the GUI element, the user is unable to add or otherwise modify the data. Stated differently, data presented in a GUI element may not be modified at runtime during the execution path of an application program. As a result, execution of a program that displays a GUI element may need to be interrupted so that the process or program that maintains functionality for obtaining the underlying data may be executed.
While specific disadvantages of existing systems have been illustrated and described in this Background Section, those skilled in the art and others will recognize that the subject matter claimed herein is not limited to any specific implementation for solving any or all of the described disadvantages.